Treatment of naphtha containing oxygenated compounds



fatenteci Oct. 2,

TREATMENT OF NAPHTHA CONTAINING OXYGENATED COMPOUNDS Du Bois Eastman, Montebello, Calif., assignor to The Texas Company, New York, N. Y., a corporation of Delaware I Application November 20, 1947, Serial No. 788,329

3 Claims. (Cl. 260-450) No Drawing.

The present invention relates to a process for the improvement in respect to anti-knock properties, gum and color stability and corrosion properties of hydrocarbon mixtures or naphtha of the type which includes oxygen-containing organic compounds, particularly those produced by the catalytic reduction of carbon monoxide with hydrogen.

Typical synthetic naphthas in question result from'passage of hydrogen and carbon monoxide in contact with a. suitable synthesis catalyst usually selected from metals of the iron group, e. g. iron, cobalt, nickel or ruthenium, under conventional and respectively established conditions of temperature'pressure and the like. Objections to many processes of this class usually include relatively low anti-knock ratings of the naphtha fractions and while more recent improvements in operating technique have resulted in a greatly improved product, the current demands for motor fuels of high octane value render it desirable to improve the octane numbers of the products by economical methods. Moreover poor gum and color stability as well as undesirable corrosion properties, due possibly to the inevitable presence of oxygenated hydrocarbon compounds in the product, require correction.

The raw productsobtained from the synthesis of hydrocarbons from carbon monoxide and hydrogen are markedly diiferent from those usually encountered in the conventional oil refinery. The most characteristic diiferences between naturally occurring oils and the synthetic Hydrocol oils result from the presence of relatively large amounts of oxygenated compounds and olefinic hydrocarbons in the synthetic product.

From about 70 to about 80 per cent of the synthesis product obtained from an efticient synthesis operation for the production of motor fuel hydrocarbons boils within the motor fuel range. The synthesis operation is more or less standardized. In general, carbon monoxide and hydrogen in molar ratio of about 1:2 is passed over an iron catalyst. The temperature is generally within the range of 500 to 700 F. and the pressure within the range of 150 to 550 pounds per square inch gauge. A powdered iron catalyst in fluidized condition is generally used. Various activators and promoters may be used with the catalyst to improve its efiiciency and selectivity.

The naphtha fraction, e. g., 100 to 400 F., is

suitable for production of motor gasoline. About 65,to about 75' weight per cent of the hydroherein is the hydrocarbon fraction, as distin guished from the water fraction, of the efiluent and. includes hydrocarbon-soluble oxygenated compounds.

Since the naphtha; fraction is the most economically desirable from the standpoint of motor fuel production, it is important that this fraction be upgraded as much as possible for use in production of finished fuels. Octane number, a measure of th anti-detonation quality of a fuel, is especially important. provides a process for greatly improving this property of the all important naphtha fraction of the synthesis products.

The present invention has for its main objective the provision of a. treatment process specifically applicable to synthetic liquid products of the foregoing class, by which a substantial improve-. ment in the anti-knockyproperties together with gum and color stability and corrosion properties may be effected at a relatively low cost. A more particular object is to provid a process which by comparison with other methods of refining, ef-

fects the foregoing improvement with a, relatively restricted loss of naphtha, under conditions of rapid treatment, with a minimum of catalyst utilization and capable of being carried out in apparatus of familiar and existing type. Other objects will be apparent from consideration of the following disclosure.

More particularly it has been discovered in accordance with the present invention that a quite substantial improvement in octane value, amounting usually to about 12 octane numbers is 'available by treatment of the foregoing synthetic hydrocarbon product, at temperatureswithin the range of about 700-900" F. by contact with a catalyst of the class consisting of bauxite, activated alumina and fullers earth. Thus, in accordance with the present invention the synthetic naphtha fraction or any other liquid fraction containing hydrocarbons and oxygenated compounds in the gasoline boiling range is caused to pass in contact with such a catalyst at the aforementioned temperature range but preferably within the range of about 800-850 F., advantageously at pressures near atmospheric.

It has also been found that the capacity of the catalyst to effect maximum improvement in octane value is limited. The effective on-stream time, prior to renewal or regeneration of the catalyst, is determined by the volume of naphtha treated. The on-stream time is the actual or average time any contact mass of catalyst is "subjected to contact with the synthetic hydrocarbon product being converted without replacement or regeneration. In short, this period represents, and, depending upon space velocity, is a measure of an overall change or alteration in the "character of the catalyst which occurs under the The present invention influence of .the reaction:, This changemay involve a deposit of som'e undesired product removable by regeneration, or some other effect arising out of catalyst use, but irrespective of its nature it has been found to bear a definite rela-' tionship to the space velocity at which the present,

reaction is carried out, as well as the total period of use before the catalyst is replaced. Foroexample, results at 5 volumes of .liquidhydro'carbon charge per volume of catalyst per hour and 4 hours on-stream time, are identical with those at 20 volumes of liquid hydrocarbon per volume naphthaltreated per volume of catalyst per cycle.

(v'q/vycyle)fis"preferably between and Underthese conditions, the improvement in octane'nluinbe'rf reaches or closely approaches maximum;

Mere, the. typically high neutralization number 'ofn'aphtha's'of the present class, as for example on theordercof about 2.5, is reduced to a vali e'ofless than 0.1 andgum and color stabilitylreach 'practicalfoptimum"values. The neutraliz ation. number is expressed as milligrams of po'ta' iumhydroxide pergram of hydrocarboil r qifireduor neutralization. In operations where; the naphtha vtreated, v./v./cycle, exceeds thera sfaboyementioned, these important improvem ts "ino'ctane value and neutralization number. rapidly vanish. There' 'is no advantage in'e'ither oct ane ,value improvement or' in convefsi'cinof oxygenated compounds from operation at le'ssj'than 1'I0'Qvl/vL/cycle. Thelincrease'd frequency'.ofbatalystregeneration imposes an un ecohoriiiciburden, Within the range of conditions disclosed, the present invention provides animproved process forimproving octane numberlof synthetic hydrocarbon fractions, presumably. as ,a -re jslilt'o'f alteration of the hydrocarbons, andielin ination of oxygen from oxygenated hy-' dr o'carbon compoundswhich are more or less. in- V evitablyassbciatedfwith the synthetic naphtha undeltreatment',

The presentfinvention is. not to be confused witht 'prior catalytic cracking and reforming process' usually carried out on gas oils or gasoline under difierent conditions," and with a material alteration inproduct distribution and yield. For example, thermally" cracked naphthas hitherto" been contacted with -clays under different 'co nd itions for reducing the sulfur content.

Also, the process knowira'fs iso'forming, higher tempratures'are employed to effect an improvement of octane rating in thermally cracked naphthas, whereas in 'an identical treatment catalytically cracked naphthas have no material responsel accompanying eliminationof objectionable acidic constituents, all without material loss of naphtha.

The efiective simultaneous: removal of my:

genated compounds and improvement octane iimi g 1 e e i it iesliy.'i lfireeeeif age iii have I unexpected, The alcohols and other oxygenated organic compounds present in'th'era'wfnaphtha in relatively large amounts are substantially com pletely converted to olefins. The unusually great improvement in octane value of the naphtha cannot be explained as resulting from removal of the. 'oxy'g'enecontaining compounds. Caustic washing of the naphtha, to remove the oxygenated compounds gives my improvement in octane vamesgrhe improvement obtained by treatment with bauxite, 'iullersearth, and the like, indicates that the hydrocarbon structure is also changed. It is believed that the primary reaction accompanying deoxygenation is isomerization of the ole'firis'b'y shifting of the double bond. This is sharply in contrast to "processes wherein the primary" reaction is cracking] Heavier fractions to cracking e. 'g., by contact with ai silicioujs cracking catalyst. The catalytic cracking simulf taneouslydeoxygenate's oxygenated compounde contained in the higherjlooiling fraction;

'By' the'pro'cess of this invention, a motor fuel of improved octane number is obtained from the product of the hydrocarbon synthesis reaction between carbon monoxide and hydrogen. The hydrocarbon product of the synthesis reaction is fractionated to obtain the desired'fnaphtha fraction boiling'within the range of from to about 400?. F. A typical naphtha fractionhas' an initial boiling point (ASTM method) "(if and an end point of 400 F.

The naphtha fraction without previous treatc ment'to remove oxygenated compoundsis passed in vapor phase over the aluminapatalyst'atj'a' temperature of 700 to 900 F.

to the naphtha vapors.

as much as possible, cracking of the hydr oca r-' bons. Other diluents may be lusedfor this'pur pose but are, .in general, less efi'ective than steam.

"The catalyst treatment resultsjin the" forma- 'j' ""tion of some polymer tar. From about 2 to about i 8 weight percent of the treated naphtha is "poly mer tar. This, is readily remove'd'from: the treat ed 'naphtha'by steam distillation.

Some lightgases arefinevitaibly produced by the catalytic treatment. These'lare produced I the result of deoxygenating the principall as y edgomeo mds Accordingly, the treated naphtha is subjected to fractionation to effect removal of undesirable higher and lower boiling constituents. The ma-' terial higher boiling than the original chargeli's removed. Obviously the resulting naphtha may be furthe r fractionated in, anydes'ired fashion depending upon the demand and specifications? for each 'grade of moto'r fuel forsale or blend; mg. V

higher pressurespas 200, pounds perlsqua're inch,

forl example, and sometimes upto "300 pgimus'per i squareinch, usually, at somewhat of a of yield, product distribution, octane, numberanfdl thelike.

The catalystsemployed are ofthe clay type which are relatively orsubstantiallyinactive forf cracking .Virgin gas oils and havi'erjthydrocap" i9i1 b =iie ii seligefef a iil iea greases 'value. The catalysts consist essentially of alumina and include activated alumina and fullers earth. The catalyst may be subjected to refining,- pelleting and the like, which are intended to remove'impurities, place the material in better physical form for use, or otherwise'render it mor suitable for the process in question.

- The invention is particularly advantageous in that it can employ with equal advantage many readily available, low cost catalyst, such as fullers earth mentioned above, bauxite, and acti-- vated alumina. In particular, a typical refined bauxite catalyst such as cyclocel or porocel, are to be preferred although activated alumina is also excellent. While for economical reasons I prefer to-use a product such as Riverside fullers earth or the aforementioned bauxite catalysts, it is to be understood that the invention is not restricted to any novelty in the catalyst, per Se, but rather concerns the application of the foregoing class of catalysts to a new and valuable process.

Catalyst sizes will not vary from the typical sizes conventional in the case of usual vaporphase catalytic processes, with due regard to the avoidance of undesirable pressure drop in the catalyst zone. Suitable catalystsizes are usually for example, from 6 to 30 mesh and conventional pelleted-catalysts may,-of course, be employed.

The invention is in no way restricted to any specific method of contacting, being applicable to batch or fixed bed operation, or moving bed catalysts and to use with fresh or regenerated catalyst. As indicated above, the on-stream time is controlled by limiting the period at which either fresh, or regenerated catalyst is subjected to the catalytic treatment in question without regeneration or replacement.

Usually it is advantageous to regenerate the catalyst after each on-stream or treating period and thereafter resubmit it to use in the treatment zone. Such a process obviously permits the use of any conventional type of apparatus whereby catalyst is permitted to reside in the reaction zone in contact with the vapor phase naphtha for the predetermined period of time, is then withdrawn, regenerated and returned. Such apparatus is exemplified by any of the conventional fluidized r moving'bed systems operating under a controlled average catalyst residence time in the treatment and regeneration zones. Among these are-the structures wherein the catalyst gravitates through the treatment chamber countercurrent to the incoming feed, and after a selected period of contact moves into a regenerating chamber. The process, however, does not require these refinements and is equally applicable to fixed bed operations where after a selected period on stream, the operation is terminated and the contents of the reactor subjected to regeneration. In fact this advantage of functioning equall well with fixed bed reactors is an important factor in permitting adaption of widely available existing equipment.

Regeneration may be carried out in any conventional-manner for catalysts of this class, for example, at temperatures of about 1050 F. and usually under pressure, as for example, 90 pounds per :square inch gauge, with the continuous recirculation of an appropriate flue gas containing, for instance, about volume per cent oxygen until carbonaceous deposits are removed. It is to be understood however that the specific meth- 0d of regeneration is immaterial to the present invention insofar as the catalyst is placed thereby in fully regenerated condition. In short the 6. temperatures and pressures are not critical and may be varied widely, and the regenerating gas may comprise steam or any other conventional medium, usually circulated in a suitable diluent to control rate of regeneration.

The catalyst is regenerated after from 10 to 30 volumes of naphtha per volume of catalyst have been treated. After regeneration the catalyst is again placed on stream.

y Example A typical crude hydrocarbon product resulting from the synthesis of hydrocarbons from carbon monoxide and hydrogen in molar proportions of about 1:2 with an iron catalyst has the follow- The high bromine number and neutralization number are indicative of the high content of olefinic and oxygenated compounds typical ofhydrocarbon synthesis products.

The crude product was cut at the 400 F.. point into two fractions:

Wt. per cent Fraction:

IBP, 400 F--- 75.3 400 F., EP; 24.7

The naphtha fraction, the physical properties of which are listed in the following table, was treated in accordance with this invention.

gThenaphtha fraction was vaporized and preheated to about 850 F. and passed over 4/8 mesh bauxite (Regular Porocel) at a space velocity of 1.02 v./hr./v. Steam. was added to the charge to give a feed containing 20.7 weight per cent watervapor. The recovered naphtha was subjected to steam distillation to remove light and heavy ends resulting from the treatment. Phy-.

sical properties of the raw, treated and steam distillednaphtha are tabulated below.

Steam Raw Treated Dis- Naphtha Naphtha tilled Naphtha Gravity, API 60. 2 61v 5 61. 7 Aniline Point, F 55. 2 82.4 84.2 Bromine Number, cgs./gm 124 113 CFRM Octane Number:

Clear 70. 9 89. 9 89. 4 1 m1. TEL/gaL. 75. 4 94. 4 94. 4 3 ml. TEL/gal.. 86.1 96. 2 96. 2 ASTM Distillation, f F.:

IBP 115 110 127 10%. 142 156 160 50% 228 226 225 90%.. 354 362 344 EP... 398 448 399 Recovery, per cent 98.0 98. 0 98-. 0

The overall yield of treated naphtha was about 88.8 weight per cent of the naphtha charged. Only 3.8 weight per cent of the charge was converted to gaseous materials. The water make was 4.3 weight per cent of the naphtha feed.

"while; the. ca bon'd pqsi on mounte t -6 weight per pe t- Little cracking or dehydrogenation took place under the operating conditions.

Referring to theda-ta in the-foregoing tabulation; it will be seen that the CFRM octane number: was increasedapproximately 14 points v he bauxite treatment, wh le e C RR 0ctane number was increasedapproximately 19 points.

The bauxite treatment resulted in increasing the end point ofthe treated naphtha due to the formation ofheavy polymer materials. These were-removed by the steam distillation of the treated naphtha. No significant increase in octane values was obtained by steam distillation. Approximately 4 per cent by volume of the treated naphtha is removed as polymer tar in the steam distillation.

The'finished naphtha which has been bauxite treated and re-run for removal of polymer tar is substantially non-corrosive and is gum-stable over long storage periods.

A number of similar naphtha fractions were treated with comparable results. Slight diiferences in composition due to differences in operating conditions in the synthesis reactor have little effect on the finally treated naphtha fraction.

-The catalyst was regenerated periodically by burning off the carbon with an oxygen-containing gas. The maximum temperature during the regeneration was approximately 1300 F. After 40 cycles the catalyst was still active.

Removal of oxygenated compounds from the raw naphtha as by extraction with ethylene gly- (301, results in lowering of the octane value and neutralization number of the raw naphtha but has no other apparent significant efiect.

From the foregoing it will be apparent that the present invention provides an effective and economical means for making an essential improvement in naphthas of the present specific class.

It is to be understoodthat this invention i generally applicable to all synthetic naphtha products of the catalytic reduction of carbon monoxide with hydrogen, in the presence of typical catalysts for this process, such as, those of the iron group, e. g., cobalt, iron, nickel or ruthenium at the well established operating temperatures and pressures which characterize the respective catalysts. As is also known the optimum conditions vary for equivalent catalysts, being in somewhat lower ranges for cobalt catalysts, typically 400 F. and around atmospheric pressure. Obviously the synthesis catalysts may include conventional additions of activators and promoters, such as alkali or alkaline earth metal oxides, alumina, titania, etc.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a process for thesynthesis of motor fuel hydrocarbons by the interaction of carbon monoxide and hydrogen in the presence of a catalystnt inin qxy en-cqmamm qm i ad Pr??- ce y th es ues a d passing Said fract on nxva o as n a m tur t steam as amount within the range of from about 5 to 0 w igh e en o th h ro a nt a m xt e into contact with fullers earth at a temperature within the range of from about 700 to about 900 F.- and at a pressurewithin the range of ;from about atmospheric to about 25 pounds per square inch gauge for a period of time effective to substantially improve the octane value of said frac; tion.

A process r the p o i nof motor. fuel hydrocarbons which comprise reactingcarbon monoxide with hydrogen at a temperature within the range of from about 500 to about 700 F. and a pressure within the range of from about 150 to about 550 pounds per square inch gauge in the presence of an iron hydrocarbon synthesis (53,031 lyst, separating from the products ofthe synthesis reaction a hydrocarbon fraction boiling within.

the range of from about F; to about 400 F. and containing oxygen-containing compounds producedby the reaction, and passing said frac: tion in vapor phase in admixture with steam in an amount within the range of from about 5 to 50 weight per centof the hydrocarbon-steam mixture into contact-with fullers earth s temperature within the range of fromabout 700 to about 900 F., under conditions of contact time efiective to substantially improve the octane value of said fraction.

3. A process for the production of motor fuel hydrocarbons which comprises reacting carbon monoxide with hydrogen at a temperature within the range of from about 500 to about 700 F. and a pressure within the range of from about to about 550 pounds per squareinch gauge in-the presence of an iron hydrocarbon synthesisca talyst, separating from the products of the synthesis reaction a hydrocarbon fraction boiling Within the range ot from about 100 F. to about 400 F. and containing"oxygen-containing.comf pounds produced by tliereaction, and'passing said fraction in vapor phase in admixture with steam in an amount within the range of from about 5 to 50 weight per cent r the hydrocarbon; steam mixture into contactwith fullers earth at a temperature within the range of fron'i about 700 to about 900 F., under conditions of contact time eflective to subst antially improve the octane value of said fraction, and subjecting the resulting hydrocarbon fraction of improved octane value to fractionation we test removal of mates rials higherboiling than the untreated hydro.- carbon feed;

D 0 E TMA REFERENCES CITED The following references are of record-in-the file of this patent:

UNITED STATES PATENTS 

1. IN A PROCESS FOR THE SYNTHESIS OF MOTOR FUEL HYDROCARBONS BY THE INTERACTION OF CARBON MONOXIDE AND HYDROGEN IN THE PRESENCE OF A CATALYST OF THE IRON GROUP, THE IMPROVEMENT COMPRISING SEPARATING FROM THE PRODUCTS THE SYNTHESIS REACTION A HYDROCARBON FRACTION BOILING WITHIN THE RANGE OF FROM ABOUT 100* F. TO ABOUT 400* F. AND CONTAINING OXYGEN-CONTAINING COMPOUNDS PRODUCED BY THE REACTION, AND PASSING SAID FRACTION IN VAPOR PHASE IN ADMIXTURE WITH STEAM IN AN AMOUNT WITHIN THE RANGE OF FROM ABOUT 5 TO 50 WEIGHT PERCENT OF THE HYDROCARBON-STEAM MIXTURE INTO CONTACT WITH FULLER''S EARTH AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 700 TO ABOUT 900* F. AND AT A PRESSURE WITHIN THE RANGE OF FROM ABOUT ATMOSPHERIC TO ABOUT 25 POUNDS PER SQUARE INCH GAUGE FOR A PERIOD OF TIME EFFECTIVE TO SUBSTANTIALLY IMPROVE THE OCTANE VALUE OF SAID FRACTION. 